1. Field of the Invention
The present invention relates to a heating device.
2. Description of the Related Art
Heretofore, in a semiconductor manufacturing process and a liquid crystal device manufacturing process, a heating device has been used in order to heat up a substrate such as a silicon wafer. The heating device includes a physical vapor deposition (PVD) device, a chemical vapor deposition (CVD) device, a dry etching device, and the like, which frequently use corrosive gas. In general, a base which constitutes the heating device is formed of ceramics from a viewpoint of corrosion resistance.
In the semiconductor manufacturing process and the liquid crystal device manufacturing process, which are as described above, a reacted film has been deposited on an outer circumferential portion of the substrate mounted on a substrate heating surface of the heating device in some cases. Here, the reacted film has been sometimes adhered to the substrate heating surface though the substrate has not been adhered thereto.
Thus, it has become difficult for the reacted film to be peeled off from the substrate heating surface when the substrate is separated from the substrate heating surface, causing an apprehension that the substrate and the reacted film may be broken.
Accordingly, for the purpose of preventing such breakage, there is known a technology, in which plural gas injection ports are provided on the substrate heating surface, and gas is injected from the gas injection ports, thereby preventing the reacted film from being deposited on the outer circumferential portion of the substrate (for example, refer to Japanese Patent Laid-Open Publication No. 2002-93894).
Incidentally, when injection amounts of the gas from the gas injection ports are increased, such increase affects generation of a grown film on the substrate, and the like, though the deposition of the reacted film on the outer circumferential portion of the substrate can be reduced. Accordingly, the injection amounts of the gas cannot be increased thoughtlessly. Hence, it is necessary to set the injection amounts of the gas from the respective gas injection ports at an amount at which the deposition of the reacted film is reduced and the generation of the grown film, and the like, are not affected.
However, according to the conventional heating device described above, the plural gas flow passages are formed by a cutting process and the like in an inside of the heating device formed of fired ceramics. Accordingly, it is difficult to enhance process accuracy of the gas flow passages. Specifically, it is difficult to uniform the respective gas flow passages in cross-sectional area, and variations occur on the injection amounts of the gas from the respective gas injection ports.
Hence, even if the injection amount of the gas from one gas injection port is set at the optimum amount, the amounts of the gas from the other gas injection ports are not optimized in some cases. Moreover, there is a problem that the injection amounts of the gas cannot be adjusted once the gas flow passages are processed and fabricated.